The radial velocity is determined from the line spectrum based on the longitudinal Doppler effect. Instantaneousness is limited by the exposure time of the spectrogram.
To determine the average tangential velocity component, positional observations separated by a large time interval (several years or more) are required. Determination of instantaneous tangential velocity is not possible.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.